Elastic properties and influence of Ba-SITE substitution on superconductivity of HoBa2Cu307-5.

The ultrasonic velocities of 10 MHz longitudinal and shear waves have been measured on HoBa2Cu3C>7-s using the pulsed-echo-overlap method. Superconducting HoBa2Cu307-s(Tczem~89 K) showed a longitudinal velocity change of 2.3 % between 80 K to 270 K and an anomalous change in slope around 230 K indicating a pronounced lattice stiffening. A similar velocity anomaly was not observed for non-superconducting HoBa2 Absolute longitudinal and shear velocity measurements on superconducting and non-superconducting HoBa2Cu307-s at 80 K showed strong influence of oxygen content on elastic properties. In addition, ultrasonic velocity measurements was performed on HoBai.ssHoi.sCusOr-s (TCzem~70 K). HoBai,85Hoi.sCu307-s showed a change in longitudinal velocity of 2.0 % between 80 K - 270 K and a change in shear velocity of around 1.5 % between 80 K -195 K. A longitudinal velocity anomaly around 230 K, similar to superconducting HoBa2Cu3C>7-s, was also observed. The velocity anomalies are explained in terms of possible oxygen-related processes and effects of Ba-site substitution.